UK light-heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive 10-round fight at the boxing arena.
But Parker had his moments, delivering effective clean blows in a match where the techniques didn't complement each other, with frequent clinching marring the contest.
Two judges had it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best display but what do champions do? They succeed," the victor said in the ring as he was faced disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a 20th pro success.
Some ringside observers believed the challenger, 31, should have been awarded the win but the contender suffered the second loss of his 28-fight professional journey.
The Champion Claims Victory in Dull Affair
Buatsi's progress has plateaued in recent years through contract problems and extended periods of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was making just his second fight at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a solid defense to barely take the cleaner stanzas.
The audience's tolerance wore thin because of frequent holding, with Parker falling to the floor various instances during clinches.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Motivates Manchester Derby Battle
In the supporting bout, Arthur defeated Rea by close verdict in a terrific local rivalry battle to win the European light heavyweight championship.
The venue fell silent for a extremely emotional tribute ahead of the contest as ten bells sounded in honor of the city's native Ricky Hatton, who died 46 years old in recently.
It was the premier televised fight night in the city since Hatton's death. As the concluding sound ended, the quiet became a roar of "there's just one Ricky Hatton".
The competition inside the ropes matched the emotion. Arthur was knocked down by a left hook flush on the face in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red attire of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was marked up soon, noticeable damage forming under his orbital area as the pair landed punishing blows.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over 12 rounds.
Arthur barely secured the decision with judges scorecards of 114-114, close margin and clearer margin, but each competitor were persistent and full of heart, exactly what their idol the legend embodied.
